Medical applications of physics

Question 1

What do we use xrays for in hospitals?

Answer 1

• To produce images and CT scans

- To destroy tumours

Question 2

Xrays are ionising, what does this mean?

Answer 2

They can damage living tissue and cells

Question 3

Xrays are absorbed more what?

Answer 3

hard things like bones and teeth

Question 4

what are CT scans used for?

Answer 4

distinguishing between different types of soft tissue as well as between bones and soft tissue.

Question 5

what frequencyies are ultrasound above?

Answer 5

20,000Hz

Question 6

what does an ultrasound scanner consist of?

Answer 6

• Transducer

- pulse generator

Question 7

what does each pulse from a transducer do?

Answer 7

• partially reflected from different tissue boundaries

- returns to the transducer as a sequence of reflected pulses

Question 8

once the pulses from the transducer are detected what happens?

Answer 8

an image is generated of the tissue boundaries.

Question 9

what are the benifits of ultrasound over x-rays?

Answer 9

• non ionising

- can be used to scan organs

Question 10

what is ultrasound therapy?

Answer 10

doctors can use powerful ultrasound​ waves to break kidney stones.

Question 11

what does angle R stand for

Answer 11

angle of refraction

Question 12

what does angle i stand for?

Answer 12

angle of incidence.

Question 13

how do we find the refractive index of something?

Answer 13

sin i
——— = n
sin r

Question 14

if there is a critical angle how do we work out the refractive index? (c = normal angle)

Answer 14

1
——— = refractive index
sin c

Question 15

when does total internal reflection happen?

Answer 15

when the angle.of incidence is greater than the critical angle.

Question 16

an endoscope is used when?

Answer 16

to see the inside of the body directly.

Question 17

a converging (convex) lens focusses parallel rays to where?

Answer 17

a focal point called the principle

Question 18

a diverging lens (concave) lens make parallel lines what?

Answer 18

spread out as though they came from the principle point.

Question 19

a real image is formed by a converging lens if the object is?

Answer 19

further away than the focus.

Question 20

a virtual image is formed with a diverging lens if the object is

Answer 20

nearer to the lens than the principle focus point.

Question 21

formula for magnification?

Answer 21

image height
———————— = magnification
object height

Question 22

a ray diagram​ can be used to find what?

Answer 22

the position and nature of an image formed by a lens

Question 23

a camera contains a converging lens

Answer 23

this produces a real image of an object.

Question 24

light is focused on the Retina by what?

Answer 24

the cornea

Question 25

the eye lens is what?

Answer 25

a variable focus lens

Question 26

the normal eye has a range of how much?

Answer 26

from 25cm to infinity

Question 27

the power of a lens is found by

Answer 27

1
—————————————– = power of a lens
focal length in meters

Question 28

converging (convex) lenses are used to correct what eye condition?

Answer 28

long sight

Question 29

diverging correcting lenses are used to correct what?

Answer 29

short sighted people

Question 30

the higher the refractive index of the glass used to make a spectacle lens

Answer 30

the flatter and thinner the lens can be.